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Manual J/Blower Door/Duct Testing

Time to replace my aging (18 years) AC systems in our 2 story house. Down stairs unit has stopped cooling completely and upstairs unit cannot keep up with demand, both are 2 1/2 ton Carrier units. I have received a couple of quotes and a Manual J was performed by one of the contracters, the other just eye balled everything and made recommendations.

My question is after reading so many posts on here, is it necessary to do a Blower Door test and Duct blaster in order to properly size the new units? None of the contactors I called, including some of the larger businesses here in Orlando, offer this service or think its necessary for proper sizing.

Without a blower door test you have to guess on the infiltration rate of the house which is a major factor in sizing correctly, with a blower door test you know exactly what the infiltration rate is and know where you can improve to reduce the infiltration this allowing smaller size equipment. Duct leakage in a typical home is 25-40% of capacity lost, you don't necessarily need a duct blaster, the blower door can tell you if the duct system is leaky but a duct blaster test is good to do. A leaky duct system would be like going to the gas station and filling up your car at 3.50$+ a gallon and having a bunch of holes in your gas tank, not a very smart move.

Thanks for the responses, jtrammel your analogy makes sense. Now its just a matter of finding someone who does these tests.

The only requirement, at least here, is that the contractor perform a Manual J. Interestingly enough, the contractor who actually did the J recommended downsizing the upstairs unit to a 2 ton and the guy who eye balled everything recommended upgrading to a 3 ton and adding another return.

Thanks, only one contractor in the area listed on these sites, will call and see if they offer these services as part of a quote or installing new systems.

Not a FPL customer, we are OUC here.

Sure about this website? What comes up is some sort of Business referral network.

Most will charge a fee for the testing because it is rather involved, takes time and the testing equipment is very expensive some will discount the testing fee off the invoice if awarded the job. Even if it costs a couple hundred bucks its well worth it when making an hvac investment. You will be more comfortable, save more on utilities and improve your indoor air quality by implementing some or all of the solutions to the problems that are found by the testing, lots of what you will find can be done by the homeowner with minimal skill and little investment (a few tubes of caulk, weather stripping, receptacle gaskets etc.) others may need to be done by hvac pros, insulators, electricians etc.

Most will charge a fee for the testing because it is rather involved, takes time and the testing equipment is very expensive some will discount the testing fee off the invoice if awarded the job.

Even if it costs a couple hundred bucks its well worth it when making an hvac investment.

You will be more comfortable, save more on utilities and improve your indoor air quality by implementing some or all of the solutions to the problems that are found by the testing, lots of what you will find can be done by the homeowner with minimal skill and little investment (a few tubes of caulk, weather stripping, receptacle gaskets etc.) others may need to be done by hvac pros, insulators, electricians etc.